According to reports, a dozen people have been killed in Wednesday's twin attacks while another 42 have been injured and admitted to 3 hospitals to receive treatment.

Jaish al-Adl (or the Army of Justice) is a Sunni militant group that has carried out several attacks on Iranian security forces mainly in Sistan-Baluchestan.

The Sunni jihadists of ISIS consider Shiite Iran to be apostates, and Teheran is deeply involved in fighting the group in both Syria and Iraq.

During the chaos, suicide bombers and gunmen stormed Iran's parliament building and opened fire on Iranian lawmakers. Again, one terrorist detonated a suicide vest and the other three were killed during clashes with security forces as they attempted to reach the upper floors of the parliament building, it said. "The depravity of terrorism has no place in a peaceful, civilized world". Within five hours, four attackers were dead and the incident was over, Iranian media said.

Jaish al-Adl claimed responsibility in April for attacks that killed 10 Iranian border guards near Pakistan.

Iran has also been expanding its influence throughout the Middle East and has aligned itself with embattled Syrian President Bashar al-Assad, who has been accused of war crimes as he fights to maintain control over his country.

Tensions have been rising between conservative US -allied Gulf Arab states, including the UAE, and non-Arab Iran over accusations that Tehran is meddling in the affairs of its Arab neighbors, a charge the Islamic Republic denies.